Gauging device and screw-down control



April 18, 1939. 5 LAMB 2,154,946

GAUGING'DEVICE AND SCREW-DOWN-CONTROL Filed Sept". 26 1935 8 Sheets-Sheet 1 INVENTOR April 18, 1939. H. s. LAMB 2,154,946

GAUGING DEVICE AND SCREW-DOWN CONTROL Filed Sept. 26, 1953 8 Sheets-Sheet 2 b N i 3 R1 W w W? m v r so I r :3 W a l v QM Q H m I 4 INVENTOR Apz il 18, 1939. H, LAMB 2,154,946

GAUGING DEVICE AND SCREW-DOWN CONTROL Filed Sept. 26, 1933 8 SheetsSheet 5 )u .525 J3 .46 J8 I INVENTOR x A ma M, M,M1M

April 18, 1939. H. s. LAMB 'GAUGING DEVICE AND SCREW-DOWN CONTROL Filed Sept. 26, 1953 8 Sheets-Sheet 4 INVENTOR April 18, 1939. s LAMB 2,154,946

GAUGING'DEV'ICE AND SCREW-DOWN CONTROL [Filed Sept. 26, 1953 8 Sheets-Sheet 5 MJM r ig. .ZZ

April 18, 1939. H, 5 B 2,154,946

GAUGING DEVICE AND SGREW'DOWN CONTROL Filed Sept. 26, 1953 a Sheets-Sheet 6 H S. LAMB April 18, 1939.

GAUGING DEVICE AND SCREW-DOWN CONTROL Filed Sept. 26, 1935 8 Sheets-Sheet 7 R O T N E V m April 18, 1939. 'H, LAMB 2,154,946

GAUGING DEVICE SCREW-DOWN CONTROL Filed Sept. 26, 1933 8 Sheets-Sheet 8 INVENTOR A 12.2% m gm ,4

aiemted Apr. i8,-l939 PATENT. OFF-ICE GAUGING DEVICE AND scanw-nown v coN'rnoi.

Howard 8. Lamb, Youngstown, Ohio, assignor to The Cold Metal Process Company, Youngstown,

Ohio, a corporation of Ohio -Applicatlon September 26, 1933, Serial No. 690,995

24 Claims.

My invention relates to metal rolling and, in particular, to an apparatus for gauging the thickness of metal while being rolled and for automatically actuating mechanism for operating screwdowns to insure .that the metal will be rolled the mill in the same time.-

to a uniform gauge.

Generally speaking, in the rolling of metal to comparatively thin gauges and, particularly, in the rolling of metal in long strips, the metal is elongated without substantial widening. I utilize this fact to determine the percentage of reduc-" tion in the gauge of material by comparing the length thereof issuing from a rolling mill in unit time with the length of the material entering The ratio of these lengths, obviously, gives accurately the percentage reduction being effected in the mill and, if the initial gauge is known, the desired final gauge may be readily produced.

This invention alsoprovides means for automatically actuating the mill screwdowns in response to the indications of the gauging mechanism to insure the production of the desired gauge in the finished material, by tightening the screwdowns if the gauge of the material issuing from the mill is excessive, or by releasing them if the gauge is too small.

' Regulators, as known to the prior art, have generally been characterized by the objection that they are subject to hunting. In other words, once a correction is initiated to rectify a departure from a normal condition, the regulator recting force, the apparatus applies a series of brief forces only to the extent required to restore normal conditions. K

In accordance with my invention, I provide differential mechanism for comparing thelengths of the material entering and leaving a four-high cold rolling mill. This diflerential mechanism may take the form of belt driven pulleys or differential gears. Preferably, I utilize a mill of the so-cailed Steckel type such asthat shown in U. S. Patent No. 1,744,018, having winding and unwinding reels for drawing strip back and forth between reducing rolls, and coolingsheaves over which the material passes in its course between reels. The differential mechanism may conveniently be connected to the cooling sheaves, which are frictionally driven by the material passing thereover at the speed of travel thereof.

A screwdown control mechanism is actuated by the differential mechanism. A friction drive connects a shaft actuated by the mechanism with 5' means for operating screwdown control contacts.

A release magnet is provided to free the contactoperating mechanism from the differential shaft after a brief period of screwdown adjustment.

A pendulum restores the contact-operating mech- 1o anism to neutral and further screwdown operation is prevented unless the differential indicator repeats its operation, demonstrating the necessity for such further adjustment of the screwdowns. V

For a complete understanding of the invention, reference is made to the accompanying drawings illustrating a present preferred embodiment of the invention with'certain modifications of parts thereof. In the drawings;

Figure 1 is a side elevation of a Steckel mill having the gauging mechanism and screwdown control of my invention incorporated therein;

Figure 2 is a diagrammatic plan view of the apparatus of Figure 1;

Figure 3 is a sectional view along the line III-III of Figure 2; I

Figure 4 is a sectional view taken along the line IV-IV of Figure 2 with parts in elevation;

' Figure 5 is a sectional view along the line V-V of Figure 4; e E

Figure 6 is a top plan view of the apparatus shown in Figure 4;

Figure 7 is a partial circuit'diagram showing how the contacts operated by the diflerential 35 mechanism control the screwdown motor;

Figure 8 is a view similar to Figure 1 showing a gauging mechanism of the diiferential gear type applied to the mill;

Figure 9 is an end view of the structure shown 40- in Figure 8;

'Flgi' e 10 is a side-elevation of the mill with the differential gear gauger, showing the side of the mill opposite that shown in Figure 8;

Figure 11 is a plan view of the diiferential 6 gear gauger with the cover removed showing parts in section along the line XI-XI of Figure 10;

Figure 12 is a side elevation of the differential gear gauger mechanism, one wall of its casing being cut away along the section line XII-XII so of Figure 11; Figure 13 is a sectional view along the line XIII-XIII of Figure 11; and

Figure 14 is a sectional view substantially. along the line XIV-XIV of Figure 12 ll The mill illustrated in Figure 1 comprisesa housing 2 having reels 3 and 4 adapted to be driven from a common power source, not shown, and to be employed alternately for reeling and paying out the material. The connection of the reels with the power source is controlled by a lever 5. Material being fed from, say, the reel 3, passes over a cooling sheave 6 and thence past wipers 'I and a guide 8 through work rolls 9. The work rolls are small undriven rolls which are backed by large diameter rolls l0 mounted in anti-friction bearings The issuing material passes over a cooling sheave l2 and thence to the reel 4. The upper backing roll I0 is adjustable vertically. It bearings are carried in cases I3 slidable in the housing and supported by spring balance mechanism 4. Wedges l5, adjustable laterally by a motor l6, determine the spacing of the work rolls 9 from one another.

The cooling sheave 6 is provided with a shaft extension l8 to which is secured a cone pulley l9, and the cooling sheave I2 is provided with a shaft extension 26 to which is secured a cone pulley 2|. The shaft extension I8 also carries a loose cone'pulley 22 and between the opposed faces 23 and 24 of the pulleys l9 and 22 there is arranged a spider 25 having rollers 26 which engage such faces. The spider 25 also carries pointers 2'| cooperating with a graduated are 28 which is held in place by brackets 29 secured to the housing 2 of the mill.

The pulleys 2| and 22 are connected by a crossed belt 36, which belt is preferably a fine but strong cord or thread, such as silk fish line. The pulleys are made very light in weight so as to have a minimum of inertia effect. The belt is kept tautby a belt tightener 3|,

The shaft extension 26 also carries a pulley 32 which is loose thereon like the pulley 22 and is connected to the pulley 9 by means of a crossed belt 33. The pulleys 2| and 32 are provided with a spider 25 having a cooperating scale 28, as above described. It is intended that the pointer at one side of the mill shall be used when the mill is being operated in one direction, and that the pointer at the other side shall be used when it is operating in the other direction.

The proper amount of friction between the faces of the cone pulleys and the pulleys 26 on the spiders is obtained by compression spring 34 backed by collars 35 on the shaft extensions l8 and 20, the compressionsprings acting through anti-friction thrust bearings 36 to press the tight and loose pulleys together.

Now assume that material is being fedv from the reel 3 to the reel 4, and that a certain reduction, say, for example, a 10 percent reduction, is desired. The steps of the cone pulleys are so arranged that the belts may be fitted into different grooves on the pulleys so that the pulley 32 will run faster than the pulley |9 in amounts corresponding to different desired percentages of reduction. In the case just given, if it is a 10 percent reduction in thickness (and no variation in width) there will be a corresponding and definite elongation. Therefore, the cooling sheave l2 will run faster than the cooling sheave 6 in a definite ratio. The belt 33 will'therefore be placed in such grooves of the pulleys I9 and 32 as will speed up the pulley 32 to give it the same number of revolutions per minute as the pulley 2| makes. Howeven by reason of the fact that the belt 33 is crossed, the pulleys 2| and 32 will be rotated in opposite directions. If'the amount of reduction is exactly that desired, the peripheral speed of each ofthe pulleys 2| and 32 at the point where it engages the rolls 26 will be the same, and therefore the rollers 26 will rotate but their axes will not be moved around the pointer 21 but will stand stationary. If, however, there is even a slight deviation from the desired percentage, the pointer will begin to move in one direction or the other, depending upon whether the reduction is greater or less than that which has been determined upon. Consequently, an adjustment of the pass must be made, as by adjusting the screwdowns.

While material is being fed from the reel 3 to the reel 4, the indicator at the right-hand side of the mill will be employed to check the reduction. It will not, however, be necessary to disconnect the indicator at the left-hand side. The pointer 21 of this indicator will'simply rotate but will be disregarded. When the mill is driven in the reverse direction the belt 30 will be placed in the proper pulley steps corresponding to the desired percentage of reduction, and the indicator at the left-hand side of the mill will be utilized.

' The bracket 3! carries a post 38 which provides a bearing for the sleeve on which the pulley 32 is mounted. A differential shaft 39 extends through the bearing 38 and is rotatable in said sleeve. The shaft 39 is driven by the spider 25,

as shown in Figure 5, and its outer end is jour-.

naled in a bearing in a post 40, also carried by the bracket-31. The post 40 supports a cross ba 4| by means of stud bolts 4|a.

A friction disc 42 is pinned to the shaft 39. A

magnetic disc 43 is rotatably mounted on the,

shaft 39 and is urged into engagement with the friction disc 42 by a'spring 44 extending from the magnetic disc to a thrust bearing 45 supported by the cross bar 4|. A pair of electromagnets 46 are mounted on the cross bar 4| on.

thrust bearing 45. The magnetic disc 43 has a contact-actuating arm 41 with a finger 48 of insulating material. A pendulum arm 49 is also attached to the magnetic disc 43 and has a bob 7 58 adjustable therealong.

' An insulating block 5| is secured to the cross bar 4| and is provided with upstanding, fixed contacts 52 and 53 and moving contacts 54. The finger 48 on the arm 41 extends between the contacts 54 and, on rotation of the disc 43, tends to actuate one of the moving contacts 54 into engagement with one or the other of the fixed contacts 52, 53.

. The manner in which the operation of the mechanism just described controls the motor l6 for actuating the mill screw-downs, will be clear from a study of Figure '7, in which some of the parts already described are shown diagrammatically and designated by the same reference numerals which have previously been employed. As shown in Figure 7, the motorl6 has a control panel 55,including forward and reverse starting relays 56 and 51, as well as other conventional starting contactors and relays, not shown. It will be understood, however, that the contactors forming part of the panel 55, under the control of the relays 56 and 51, control'the energization of the motor |6 from a power circuit 58 to efiec the differential shaft 39 willturn counterclock;

this result is to make the magnets of the slow wise if the gauge of the material issuingfrom the mill is less than that required by the setting of the belt on the shaft. This rotation of the shaft will be immediately communicated to the magnetic disc 43 through the friction disc 42 and angular movement of the arm 41 causes the left hand contact 54 to engage contact 52. As will be apparent from a study of Figure '7, this operation completes a circuit for energizing the relay 55 of the control panel 55. The relay 58, when energized, through various other relays and contactors, not shown, as is well known in the art, operates to start the motor IE to drive the screwdowns so that the top roll is adjusted downward. It will be observed that the magnets 46 are connected in parallel .across the armature of the motor i5. As soon as the motor is energized, therefore, the magnets likewise will be energized to withdraw the magnetic disc 43 from engagement with the friction disc 42. The pendulum bob 50 immediately restores the disc 43 to neutral position and the circuit for the relay 56 is thereby broken and the motor I6 is stopped. The magnets 45 are also de-energized, and the disc. 43 reengages the disc 42. It is obvious that adjustment of the operating time of the relays, contactors and magnets 45 will permit the motor IE to effect a slight adjustment of the screwdowns before it is stopped. One way of accomplishing response type by means of a shading coil, thus introducing a certain time delay in the building up of the fuil ilux thereof.

If the initial adjustment of the screwdowns is suillcient toprevent further rotation of the differential shaft 38, no further adjustment occurs. If

- not, however, the differential shaft again rotates in the same direction and a further adjustment is made, and soon until the proper relation of the speeds of the material entering and leaving the mill is brought about.

If the gauge of the issuing material is too small, obviously, a clockwise rotation of the shaft 88 will result and the right hand contact 54 will engage the contact 53 to energize the relay 51. This relation causes a reve se operation of the motor ii to raise the screwdowns. This operation, of course, is of the step-by-step type, as above described.

It will be apparent that a duplicate set of contacts and contact-actuating mechanism will be required on the left hand slde,of the mill, as shown in Figures 1 and 2. so that proper screwdown operation will be obtained for both directions of movement of the material. The contacts may be connected in parallel to the-relays of the panel 55 and alternately inserted and removed from the circuit by a simple switching'operation by obvious means, not shown. The retracting magnets of the device not in use may be continuously energized during the reversing period by any suitable switch mechanism, to free the contact operating disc from the differential shaft.

.A preferred form of the gaugingmechanism .per se, which is also adapted for operating the screwdown controlling contacts. is shown in Figures 8 through 14; The differential mechanism is mounted in a case-8D secured to one side of the mill housing onJ bracket 5|. This form of the invention is similar in principle to that already described but differs therefrom in that the differ- 'ential mechanisni is made up of gears instead ofpulleys and belts. -T he gear form of the device presents certain advantages in that it avoids any slippage or change in tension of 'the belts. 'A

positive drive is thus assured which renders the gear device more accurate than the pulley and belt mechanism.

The mill to which thediiferential gear mecha nism is applied, is similar in general to.- that shown in Figure 1, and corresponding parts are indicated by the same reference numerals. 1 provide, however, for utilizing the same gauging mechanism regardless of the direction of move ment of the material. Instead of duplicating the' gauger mechanism, I reverse the drives of the two ends thereof. A differential gear reversing lever 62 is journaled in hearings on the bottom of the bracket 8 I. The end of the lever is connected by a link 53 to a crank 83d on a shaft 64 extend-- ing across the mill and journaled-in the housings. A crank 85 for operating the rod 84 is connected to the main reversing lever 5 by a link 68. When the mill is reversed by operation of the lever 5,

'therefore, the gauging mechanism is automat1-'- cally actuated so that it is operative for the re-v :verse movement of the material.

As in the pulley and belt mechanism, it is necessary to compare the lengths of the material entering and issuing from the mill. In the pre-' ferred form of 'the'apparatus, I provide helical gears 81 mounted on extensions of the shaftsof the cooling drums. Gear cases 58 mounted on the mill housings provide bearings forshafts 69 hav-- ing helical gears 18 thereon .meshing with the gears 51. The shafts 88 at opposite ends of the mill are connected to shafts H and I2 journaled insuitable bearings I8 on the. bottom of the case 58, by means of universal Joints and connecting shafts I4.

Referring now particularly to Figures 11 through 14 for a disclosure of the details of the differential gear gauger, it will be seen that the shafts II and 12 are provided with gears 15 and 15a respectively. Each of these gears is provided 49 with a clutch member adapted to cooperatealternately with one of two similar members on the ends ofa shaft 18 journaled-in movable bearings 11. The shaft I5 is provided with a gear I8 for a purpose which will appear later.

Gears I8 and 88, meshing with gears 15 and- I5w, respectively. are mounted on suitable shafts also journaled in the bearings I8. These gears also have clutch members for cooperating alternately. with corresponding members on a shaft 8| which is similar in general to the shaft." in that it has movable bearings 82. The shaft 8| is provided with a sleeve 88 splined thereto, the opposite sides-of which rotatably support upstanding bearing posts 84. A gear 85 is keyed to the sleeve 83 'A nestcf gears 85 of slightly different 7 sizes are secured to a shaft mounted in suitable bearings at the upper ends of the posts 84.

.bottom' of the casing 88. Adiiferential gear 88 having a spur gear 88 formed integral therewith, is mounted on a suitable shaft carried Y in the'bearing post 88. The gear 80 is in mesh with the gear .18 on theshaft 18. A differential shaft 9| is iournaled in .thebearir gs 8 1 and 88 and in a bearing 82' in'the end wall of the casing; A differential gear 88 haviL, a spur gear 84 integral therewlthgis iournaled on the shaft 8|; The spur gear-841s adapted 0 mesh with one. of the gears of the-nest 85. A differ-v ential pi n 85 is iournaled in a spider 88 keyed to the shaft 8|. The pinion 85 is in mesh with the gears 89 and 93.- i I With the parts in the positions shown inl igure 11,- it will beapparent that the shaft 16 will be driven at a speed proportional to that of the left hand cooling sheave shown in Figure 10. At the same time, the shaft 9| will be. driven at a speed proportional to that of the right hand cooling drum. The drive for the shaft 16, of course, is effective through the engaged clutch members on the shaft and the gear '55. The drive for the shaft includes the gears a and 90 and the clutch members on the gear and the shaft 8| itself.

Assuming that the material is moving through the mill in the direction of the arrow shown in Figure 10, the shaft ill will be driven at a speed proportional to that of the material issuing from the mill. The shaft I6 will be driven at a speed proportional to that of the material entering the mill. The differential gear 89 will be driven through the spur gears 18 and at a speed proportional to that of the entering material. The differential gear 93 will be driven by the spur gear and one of the gears of the nest .96 in mesh therewith at a speed proportional to that of the issuing material. Because of the interposition of the gear nest 86, the gears of which are smaller than the gear 94, the latter is driven at a speed which is equal to the speed of the gear 99 as long as a predetermined ratio exists between the speeds of the material entering and leaving the mill. This ratio is the same as that between the sizes of the active gear of the gear nest and the gear 94. By providing in the gear nest 06 a plurality of gears, the pitch diameters of which have the same ratios to the pitch diameter of, the gear 94 as the gauge of the material leaving the mill to that of material entering the mill, forthe various desired percentages of reduction, therefore, the differential gears will be driven at the same speed in opposite directions, of course, as long as the speed of the material leaving the mill bears a certain ratio to the speed of the material entering the mill,.

indicating that the selected percentage reduction in gaugemdetermined by which gear of the nest 86 is in mesh withthe gear 94). is being effected. As long as the gears 89 and 93 rotate at the same speeds in opposite directions, of course, the pinion rotates, but the spider 96 and the shaft- 9| are stationary. Any difference 1 in the speeds of the differential gear, of course, will be reflected immediately by a corresponding rotation'of the spider and differential shaft. An

indicator disc 91 mounted on the outer end of the shaft 9I, provides a readily visible showing of the difference in speeds. applied to the peripheral face of the disc, or otherwise, to facilitate observation.

Yr Means are provided for adjusting the position of the gear nest to set the indicator for different. percentages of reduction, including a vertical shaft 99 having a, fork 99 extending radially thereof. The left'hand bearing post 94, as observed in Figures 11 and 12, is provided with a toothed projecting finger I00 adapted to cooperate-with a plate II-secured to the bearing post 91 and having a notched edge. The notches in the edges of the plate I 0| are arranged in number and depth to permit the engagement of any one of the gears of the nest' 96 with the gear 94,, The gear nest as a whole is rotatable about the shaft M, of course, and isnormally urged toward the gear 94 by a spring I02 suitably secured at one end to the post 99 and attached to a pin fI03'projecting inwardly of the right hand'bearingpost 94.

The shaft 99 is bored out to receive a push Markings may be operates with a projection I06 extending from the toothed member I00. When the push rod I04 is depressed, the outer end of the finger I06 is raised and the gear nest and its bearing posts are then swung clockwise on the shaft 8I so that the gear nest is clear of the gear 94. The toothed member I00 is also cleared from the notched edge of the plate IOI. Rotation of the shaft 99 by means of a knob 98a, for example, moves the gear nest,-its bearing posts, and the sleeve 93 along the shaft 8I.

When a selected gear of the nest 96 has been alined with the gear 94, release of the push rod permits the spring I02 to swing the gear nest counterclockwise so that the selective gear thereof engages the gear 94. Simultaneously, the

toothed member I00 engages the notched edge of the plate IN to lock the gear nest in adjusted position. A pointer I01 secured to the shaft 96 and cooperating with a. scale on the cover of the casing 60 serves to indicate the proper positions of the gear .nest for putting the several gears thereofyin mesh with the gear 94. It will be apparent that almost any thickness of hot rolled strip may be reduced to the desired finished gauge by a proper selection of the percentages of reduction for the several passes through the mill. For the convenience of the operator, the adjustments of the mill to reduce the various gauges of hot strip to the various finished gauges will appear on a chart which will be provided; Indicating the adjustments necessary for all possible cases.

It will be apparent that the differential shaft 9| of the apparatus shown in Figures 8 through 14 will operate in exactly the same manner as the shaft 39 of Figures 1 through '7, to actuate the screwdown control contacts. These contacts have been shown associated with the differential gear mechanism only in Figure 11, but a repetition of the description thereof is unnecessary, since the construction and the manner of operation are identical. As will be apparent from Figure 11, the cross bar 4I is attached to the end wall of the casing 60.

' It will be apparent that the shaft 8| must always be driven by the cooling drum on the side of the mill from which the material issues.

' When the direction of travel of the material is II and I2 to the shafts I6 and 9| must be reversed. The reversing lever 62 cooperates with a crank I 08. The crank is of U-shape and serves to actuate a pivot bar' I09 resting on the floor of the casing 60 for angular movement about a central pivot. The bearings 11 and 92 for the shafts I6 and BI are carried on slide rods H0 and II '01;

supported in bearingsJ I I. When the crank I09 is in the position shown in Figure 11, the bearin s .of the shaft I6 are shifted to theleft, and

those of the shaft 8| to the right. The gear" is thus connected to the shaft 16 and the gear 80 to the shaft'OI. Reverse movement of the crank I08,'which is efl'ected as previously de scribed, by the operation of the main reversing lever- 5, swings the pivot bar I09 in a clockwise direction, as shown in Figure 11,'and causes the clutch members A to engage whilfith previouslyjengaged clutch members'on theshaftand the gear I5 are sepa rated. At the same time, the gear I9 is connected tothe shaft ill by the engagement of the '10 gear 1 5a and the'shaft I6 clutch members and the shaft is made independent of the gear 80. Upon reverse travel of the material, the device will operate in the manner previously described to indicate variations from the selected rate of reduction.

It will be apparent from the foregoing description that the invention provides a highly eflicient and satisfactory means for determining the de partures of the rate of reduction from a preselected value. Theautomatic screwdown control mechanism, furthermore, makes it unnecessary for the operator to concern himself with the adjustment of the rolls. If the strip comes through the mill too thick, the screwdowns will be properly adjusted and the selected rate of elongation will be maintained. Similar adjustment in the opposite direction is eifected' automatically if the material is too thin. The screwdown control itself is characterized by a quick response and by freedom from hunting. The rate of elongation may thus be maintained accurately within narrow limits at all times. The method and apparatus for measuring the rate of reduction of the material by comparing the speeds of the material entering and leaving the mill, are obviously a marked improvement over prior means for accomplishing similar results. The measuring apparatus disclosed is remarkably accurate and at'the same time, is so simple in construction as to render its manufacture at a rea- .trolled' by the gauger for tightening and releasing the screwdowns.

2. The combination with a rolling mill having screwdowns, and'means for comparing the speed of the material entering the mill with the speed of the material emerging from the mill, of means actuated by the speed comparing means for operating the screwdowns.

3. The combination with a rolling mill having screwdowns, and a differential gear mechanism for comparing the speed of the material entering the m'illwith the speed of the material emerging from the mill, of means controlled by said difierential mechanism for controlling the operation of the screwdowns.

4. Apparatus for controlling the adjustment of rolling mill screwdowns comprising a shaft, .differential gearing for rotating the shaft when the relation of the speed of material issuing from the mill to the speed of material entering the mill varies from a predetermined value, contacts operated by said shaft, and a screwdown motor controlled b said contacts. 5. Apparatus for controlling the. screwdowns of a rolling mill comprising means responsive to a the contact-operating means from said firstmentioned means.

6. In a screwdown control for rolling mills, means responsive to the ratio of the thicknesses of material before and after passing through the mill including a shaft, a screwdown motor, con

- tacts for controlling the screwdown motor, means actuated by the shaft and normally secured thereto for operating the contacts, and electromagnetic means for freeing the contact-operating means from said shaft.

'7. A differential gauger for measuring the differential gears and a differential pinion meshing therewith, means for driving said gears at speeds proportional to the entry and exit speed of the material, the drive for one of said gears including a speed change gear, and an indicator shaft actuated by movement of said differential pinion.

9. A differential gauger for measuring the thickness of material traversing the rolling mill comprising a shaft, means for driving the shaft at a speed proportional to that of the material entering the mill, a second shaft, means for driving the second shaft at a speed proportional to the speed'of material leaving the mill, the speed of the second shaft being difierent from that of the first, speed change gears on said second shaft, differential gears driven by the first shaft and by one of the speed change gears on the second shaft, a differential pinion meshing with said differential gears and an indicator actuated on movement of said pinion. Y

10. A differential gauger for measuring the thickness of material traversing the rolling mill comprising a shaft, means for driving the shaft at a speed proportional to that of the material entering the mill, a second shaft, means for driving the second. shaft at a speed proportional to that of the material leaving the mill, differential gears driven by said shafts, a differential pinion meshing with said gears for actuating an indicator, and means for interchanging the connection between said shafts and theirdriving means.

11. Apparatus for gauging the thiclmess of material traversing the rolling mill comprising differential gears, a differential pinion meshing with saidgeai's, an indicator actuated by movement of said pinion, and means for driving said gears at speeds proportional to those of the material entering the mill and the material leaving the mill, the drive for one of said gears including a ferential gearing, means for'driving one side of .1

the other side of the gearing at a speed proportional to that of material leaving the mill, and

means for interchanging the drives of the respec- 'tive sides of the differential gearing.

, 13. The apparatus definedby claim 12 wherein means for comparing the entering and exit speeds said interchanging means comprises a plurality of clutches between the driving means and the differential gearing, and means for engaging and with a gear on one side of the differential gearing.

15. In combination with a rolling mill, means for measuring the. effective surface speed of a work piece as it enters said mill and as it leaves said mill, and automatic means for actuating the screwdown of said mill in accordance with said measurement.

16. In combination with a rolling mill, means for measuring the effective surface speed of a work pieceas it enters and as it leaves said mill, means for causing the differential actuation of a member in accordance with said speeds, adjusting means permitting the selection of a desired speed ratio, and means actuated by said member to control the screwdownof said mill.

17. In combination with a rolling mill having a motorized screwdown, meansfior measuring the effective surface speeds of a work piece as it enters and leaves said mill, means for causing said measurements to be subtractively effective dao cause movement'of a member, contacts associ: ated with said member and an electric means associated with said contacts to energize the screw-. down motor in accordance with the movements of said member.

18. The combination with a rolling mill having screwdowns and a driving motor therefor, of

of the material traversing the mill and control ling the screwdownmotor, and means independent of said motor. for stopping the motor after a fixed, predetermined, short interval.

19. The combination with a rolling mill hav-- ing screwdowns, a motor for adusting the screwdowns, and means responsive to the ratio of entering and exit speeds of the material traversing the mill for automatically initiating operation of said motor, of means for stopping the motor after a fixed, predetermined, short interval of 1 operation.

20. The combination with a rolling mill, a gauger having a reversible member operable in response to a comparison of the entering and exit speeds of material traversing the mill, screw-.

downs for the mill, a motor adapted to operate the screwdowns, and contacts controlling the operation of said screwdown motor operable by said reversible member.

21. The apparatus defined by claim 20, characterized by contact-operating means releasably attached to said reversible member, and means for freeing the contact-operating means from the reversible member within a predetermined, fixed time after operation of one of said contacts.

22. The apparatus defined by claim 20, characterized by contact-operating means connected screwdowns for controlling the thickness of the material issuing from the mill, means for comparing the speeds of the material entering and leaving the mill, means controlled by said means for adjusting the screwdowns, and means for arresting said screwdown operating means after a predetermined time subsequent to the commencement of its operation.

HOWARD S. LAMB. 

